Process for obtaining photographic images



Patented Mar. 18, 1930 UNITED STATES;

PATENT OFFICE EUGENE GAY, or LYON, rRANoE N Drawing. Application filed October 14, 1926, Serial No. 141,671, and in France October 23, 1925.

In the specification filed upon a co-pending application Serial No. 141,670, dated 14th October, 1926, a process is described for obtaining photographic images based upon the formation of azo dyes by reaction of diazo bodies sensitive to the action of light upon phenols or amines in the presence of alkali.

The invention consists in adding to the diazo bodies forming the sensitive film or layer certain substances which produce phenols or naphthols by the action of alkalies, which permits sensitive films or layers to be obtained which can be developed by the simple action of alkaline substances (vapours of ammonia or alkaline baths).

It has been established that the speed of reaction of diazo bodies with phenols which is high in an alkaline medium is often far from negligible in a neutral medium and this constitutes an obstacle to the use of mixtures of diazo bodies with phenols for obtaining sensitive films or layers suitable for developing by the simple action of alkalies.

This disadvantage can be remedied up to a certainpoint by acidifying the mixture. Thus the speed of the reaction is diminished but this effect is secured to the detriment of the preservation of the substance of the support such as paper that is employed. In fact this leads with certain diazo bodies and certain phenols to the use of an inadmissable quantity of acid. 1 i

The difliculty referred to is obviated in replacing phenol or naphthol by one of its acetyl derivatives capable of regeneration under the action of the alkali employed during 'the development, which is introduced only at the moment of development.

40 Theacetyl derivatives of phenols, di and tri-phenols, naphthols, dioxynaphthalines and amidonaphthols lend themselves particularly well to obtaining stable mixtures With diazo bodies in a neutral medium. The phenolic estersderived from formic acid, oxalic acid or benzene-sulphonic acid and generally the aromatic bodies R. 0. Ac. (in which R represents a benzene or naphthalene nucleus substituted or not substituted and Ac. denotes an acid radicle) may be employed. Certain of these products being slightly soluble in water their sulpho or carboxyl derivatives may be used or even the alkaline salts of these derivatives. The diazo body and the acetyl derivative of phenol or naphthol are mixed and the mixture used for the formation of the sensitive film or layer on the support, so that on exposure to light under a drawing or the like, the imagefin azo colour,

is produced by development of the exposed film or layer by means of an alkali only.

Thus, tor example, there is added to one litre of a bath of the diazohydroquinonedimethyl ether obtained according to'the directions given in the specification filed upon the said co-pending application, 30 gr. of 1-8-diacetyldioXynaphthalene-3-G-disulphonic acid and one litre of water.

A sheet of paper or-other convenient support impregnated in this bath, dried and exposed to light under a transparent design, until the parts not protected by the'design are decoloured, yields by development with the ammonia vapour a positive violet red image. The colour which constitutes the image is identical with that obtained by coupling of the diazohydroquinonedimethyl ether and the chromotropic acid, that is to say, that it has the property of giving lakes with metallic salts, which permits of varying the shade by trial either in toning them in baths of metallic salts after development .or in introducing these salts in the sensitive bath.

I claim:

A process for obtaining. a photographic ii'nage of the kind described, consisting in impregnating a substance having a surface adapted for the reception of a photographic image in a bath of I-S-diacetyldioxynaphthalene-3-6-disulphonic acid and diazohydroquinonedimethyl ether, drying the said substance and exposing the substance under a transparent design having substantially opaque parts and developing by an alkali to yield a positive violet red image, substantially as hereinbefore described.

EUGENE GAY. 

